In forming power or signal distribution systems, it is necessary to provide interconnections between various members or components of the system. Generally the interconnections are provided by electrical connectors having one or more electrical contact terminals therein.
A major requirement of any connector system is that it be reliable and stable over a life span that may be as long as 10 to 20 years. In many integrated circuit systems there can be no more than a 5 percent voltage drop through the system. Thus each connection can only have a very small percentage of the total drop. It is essential therefore that the connectors be designed to minimize the millivolt drop and to remain stable throughout the life of the system.
With advances in technology, the amount of total termination resistance, which includes a combination of bulk resistance, constriction resistance and crimp resistance, permitted by a system is being reduced and in many systems the total termination resistance is in the magnitude of 10 milliohms or less. It is necessary therefore to design contact members and in particular power contact members that have a very low millivolt drop at each point of termination. In addition, the millivolt drop, which is a function of the resistance of the contact member, should not increase very much over the life of the contact. In order to meet the design requirements, it is necessary to drop the bulk resistance of the contact member as low as possible, lower the "constriction resistance" that is the resistance between the contact points or beams of the contact member and provide a termination to a wire that has a low resistance and is stable.
In designing the mating portion of a power contact member, it is most desirable to use a plurality of spring contact arms which will provide a plurality of parallel paths thus reducing the millivolt droppage of the total contact member. The material selected for the contact, therefore, must be highly conductive yet have sufficient mechanical properties and exhibit sufficient tensile strength that allows beams to be formed having a small cross section and a very low stress relaxation so that the contact beams will continue to exert sufficient normal force over the life of the contact.
U.S. Pat. No. 2,704,358 discloses a contact of the prior art used for power systems having a solid barrel portion, a transition portion and a contact area. The width of the material used in the transition area between contact area and the barrel portion is narrow. The current flowing through this contact area therefore must flow through the narrow transition portion and into the larger body and contact area, thus raising the resistance and thereby the temperature in the transition portion. The very small cross sectional area of the transition portion of the contact terminal in effect may act as a fuse because it can overheat. It is desirable, therefore, to provide a contact terminal or member that will have an essentially constant cross sectional area throughout the length of the terminal.
U.S. Pat. No. 2,535,013 discloses a connector having a crimpable power contact terminal having a solid barrel portion made by brazing the seam of a formed member. Solid barrel terminals may also be made by machining as known in the art. A brazed seam barrel is suitable for terminal members such as those having blade type contact portions or a terminal wherein a wire is bolted to contact portion. The brazed seam barrel, however, is not suitable for the usual contact members having compliant beams. The high temperature required to braze a material having a high conductivity of heat as well as electricity will soften or anneal the metal in the flexible beams contact portion thus removing the resiliency of the beams and reducing the normal force. It is desirable, therefore, to find a means for forming a crimpable barrel connector that will in essence act as a solid member without requiring brazing or joining of the seam or a separate solid sleeve member disposed over the seam.